1. The Field of the Invention
The present invention relates to fiber optic catheter assemblies used as a waveguide for carrying laser light energy. More particularly, the present invention is directed to a novel laser catheter assembly utilizing a unitary connector for interconnecting an optical fiber with a laser light source.
2. The Prior Art
Lasers have become increasingly important in surgical applications since the first use of an argon laser in the treatment of diabetic retinopathy in 1965. Success with the argon laser eventually led to research into the possible uses of other commonly available lasers, such as the CO.sub.2 and Nd-YAG lasers, each different laser having particular characteristics which make it useful in different surgical settings.
Lasers operate on biological tissues to different degrees depending upon whether the particular laser beam is absorbed, reflected, scattered, or transmitted by the tissue. The primary effect of laser light on biological tissues is thermal energy caused by absorption. Laser beams from different types of lasers are typically absorbed by different tissues in the body. Depending upon the amount of energy in the laser beam, this thermal energy can act to vaporize the tissue, or merely to coagulate it.
With the development of optical fibers, even greater flexibility and increased applications for laser surgery became apparent. This was especially true of the argon laser because of certain very useful properties: it is highly absorbed by melanin and hemoglobin, yet is only weakly absorbed by other body tissues. Further, the argon laser beam may be transmitted through small-diameter optical fibers, allowing great maneuverability and precision during surgery. As a result of these advances, argon lasers are currently used in many applications in plastic surgery, dermatology, neuro-surgery, gastroenterology, urology, bronchoscopy, and otorhinolaryngology. Argon lasers have been shown extremely effective in many situations adaptable to endoscopic surgery and requiring general hemostasis, coagulation of vascular lesions, or coagulation of mucosal lesions.
In the past, it has been thought necessary to utilize very complex connectors for interconnecting the optical fiber with a laser source, these connectors consisting of a number of very carefully machined metal parts adapted to fit together with great precision so as to precisely align the optical fiber with the laser beam. Some of the prior connectors have even incorporated a series of lenses to focus the laser beam onto the end of the optical fiber. Conventional connectors also incorporate a convex gold collar disposed about the end of the optical fiber so as to provide an inert reflective surface for the laser beam in the event it is misdirected away from the end of the optical fiber.
While these prior connectors have proven effective, they are disadvantageous for several reasons. For instance, prior connectors are very expensive to manufacture because of the number of parts that must be carefully produced so as to fit together to extremely close tolerances; even a very slight misfit will result in misalignment of the optical fiber and the laser beam. In addition to the significant expense incurred in machining these parts to such fine tolerances, the expense is compounded due to the fact that when one of these expensive parts does not meet these tolerances, it must be discarded. Further, the cost of materials is quite significant when manufacturing conventional couplers since they are constructed from alloy metal components, and at least one part involves the use of gold.
The disadvantage of the high cost of these conventional connectors is somewhat offset by the fact that they are reusable. Unfortunately, the optical fiber held by these connectors is typically in need of repair or replacement after only a few surgical operations, an operation which requires disassembly of the connector, followed by reassembly of the various connector components together with the new or repaired optical fiber. Because of the need for extremely precise positioning of the optical fiber within the connector it has been necessary heretofore to send the entire laser catheter assembly back to the factory for repair or replacement of the optical fiber. Inasmuch as the turnaround time for these repairs is generally several weeks, it has proven necessary for hospitals performing a large number of laser surgical operations to have a large number of laser catheter assemblies in its inventory. This has required a very large capital outlay and a significant inventory cost, which in turn results in large costs which must be passed on to the patient. Use of these conventional connectors also causes difficulty to hospital administration in allocating costs attributable to capital depreciation, repairs, sterilization, and the like.
Even more significantly, reuse of a laser catheter assembly incorporating a conventional coupler exposes patients to substantial risk. Although in some surgical procedures the laser catheter is merely grasped by the fingers of the physician at a position near the distal end of the catheter and wielded much like a light pen, in many cases it is necessary to actually insert the catheter within a body cavity, usually in connection with an endoscope.
Accordingly, it is of paramount importance to insure that the laser catheter assembly is sterile when it is to be inserted into a surgical site. However, the use of a multiplicity of parts in the conventional connector provides many locations where foreign material can accumulate, thus making it difficult to maintain proper sterility as the connector is used time and again.
This is compounded by the fact that a coolant is typically introduced into the connector and directed along the length of the optical fiber before venting at the working end of the catheter. This coolant often serves as a carrier for bacteria or the like from the connector and to the surgical site.
Additionally, as a conventional connector is disassembled and reassembled over its useful lifetime, small amounts of the material from which the connector is constructed abrade or otherwise break loose from the connector and may be carried into a patient along with coolant.
Thus, it will be appreciated that it would be a significant advancement in the field of laser catheter technology if a simpler and less expensive laser catheter assembly and connector could be provided that would properly position the optical fiber in the path of the laser beam and would reduce the risk caused by the present practice of reusing the laser catheter assembly.